unofficial mirror of bug-guile@gnu.org 
 help / color / mirror / Atom feed
* bug#40744: guile-2.2.4 (integer-length 0) erroneously returns 0, not 1
       [not found] ` <20200425213350.GA10462@LionPure>
@ 2020-04-28 18:08   ` Björn Höfling
  2020-04-28 18:41     ` Björn Höfling
  0 siblings, 1 reply; 4+ messages in thread
From: Björn Höfling @ 2020-04-28 18:08 UTC (permalink / raw)
  To: Bengt Richter; +Cc: 40744-done

[-- Attachment #1: Type: text/plain, Size: 632 bytes --]

On Sat, 25 Apr 2020 23:33:50 +0200
Bengt Richter <bokr@bokr.com> wrote:

> Apologies for my faux pas ;-/
> 
> This was not a guix bug, and you have rightly ignored my report.
> (now submitted to bug-guile, with hopes of nz human acks :)
> 
> (I guess it will get a new number, so 40744 can be closed?)
> 
> (BTW, no offense intended in addressing you as "guix/guile
> bug-squashers" ;-/) 

There is a significant overlap between both groups and all like bugs to
be gone :-)

Bugreport was re-opened under the guile package here:

https://debbugs.gnu.org/cgi/bugreport.cgi?bug=40855

Closing this one.

Björn

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 195 bytes --]

^ permalink raw reply	[flat|nested] 4+ messages in thread

* bug#40744: guile-2.2.4 (integer-length 0) erroneously returns 0, not 1
  2020-04-28 18:08   ` bug#40744: guile-2.2.4 (integer-length 0) erroneously returns 0, not 1 Björn Höfling
@ 2020-04-28 18:41     ` Björn Höfling
  2021-07-16  3:01       ` Rob Browning
  0 siblings, 1 reply; 4+ messages in thread
From: Björn Höfling @ 2020-04-28 18:41 UTC (permalink / raw)
  To: Bengt Richter; +Cc: 40744

[-- Attachment #1: Type: text/plain, Size: 323 bytes --]

On Tue, 28 Apr 2020 20:08:10 +0200
Björn Höfling <bjoern.hoefling@bjoernhoefling.de> wrote:


> Bugreport was re-opened under the guile package here:
> 
> https://debbugs.gnu.org/cgi/bugreport.cgi?bug=40855
> 
> Closing this one.

Oh, I didn't realize they were merged. So, I reopened them again :-)

Björn

[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 195 bytes --]

^ permalink raw reply	[flat|nested] 4+ messages in thread

* bug#40744: guile-2.2.4 (integer-length 0) erroneously returns 0, not 1
  2020-04-28 18:41     ` Björn Höfling
@ 2021-07-16  3:01       ` Rob Browning
  2021-07-24 17:12         ` Bengt Richter
  0 siblings, 1 reply; 4+ messages in thread
From: Rob Browning @ 2021-07-16  3:01 UTC (permalink / raw)
  To: Björn Höfling, Bengt Richter; +Cc: 40744


Hmm, the zero result appears to be intentional, i.e. it's mentioned in
the examples here:

  https://www.gnu.org/software/guile/manual/guile.html#Arithmetic

and is also specified by Chez Scheme and SRFI-60:

  https://www.scheme.com/csug8/numeric.html
  https://srfi.schemers.org/srfi-60/srfi-60.html

-- 
Rob Browning
rlb @defaultvalue.org and @debian.org
GPG as of 2011-07-10 E6A9 DA3C C9FD 1FF8 C676 D2C4 C0F0 39E9 ED1B 597A
GPG as of 2002-11-03 14DD 432F AE39 534D B592 F9A0 25C8 D377 8C7E 73A4





^ permalink raw reply	[flat|nested] 4+ messages in thread

* bug#40744: guile-2.2.4 (integer-length 0) erroneously returns 0, not 1
  2021-07-16  3:01       ` Rob Browning
@ 2021-07-24 17:12         ` Bengt Richter
  0 siblings, 0 replies; 4+ messages in thread
From: Bengt Richter @ 2021-07-24 17:12 UTC (permalink / raw)
  To: Rob Browning; +Cc: Björn Höfling, 40744

Oops, forgot to reply-all -- sorry about the dup, Rob ;/

On +2021-07-15 22:01:32 -0500, Rob Browning wrote:
> 
> Hmm, the zero result appears to be intentional, i.e. it's mentioned in
> the examples here:
> 
>   https://www.gnu.org/software/guile/manual/guile.html#Arithmetic
> 
> and is also specified by Chez Scheme and SRFI-60:
> 
>   https://www.scheme.com/csug8/numeric.html
>   https://srfi.schemers.org/srfi-60/srfi-60.html
> 
> -- 
> Rob Browning
> rlb @defaultvalue.org and @debian.org
> GPG as of 2011-07-10 E6A9 DA3C C9FD 1FF8 C676 D2C4 C0F0 39E9 ED1B 597A
> GPG as of 2002-11-03 14DD 432F AE39 534D B592 F9A0 25C8 D377 8C7E 73A4

I tried to make a pitch for (integer-length 0) =-> 1 in
[1]    https://lists.gnu.org/archive/html/bug-guile/2020-04/msg00027.html
though I now think integer-length is a useful measure of mathematical
integervalues that can be generalized to any rational numbers and
complex numbers with rational real and imaginary parts.

Also their printed representations can have any rational radix other
than 1 and negative generalized integer-lengths can be meaningful for
length of 1/x vs x (which brings in the zero issue).

For the "integer-length" I compute in [1], I would now suggest an alternate
name: integer-digits -- the number of concrete digit-value representations
it take to represent the polynomial coefficient values in the mathematical
polynomial series.

I should update [1] to reflect what I am saying here to remove complaints
about integer-length 0 etc and talk about integer-digits (or maybe
rational-digits or even numeric-digits?)

I think scheme's integer-length basically solves for minimum L in
in a mapping of rational numbers (limited to integers in its case)
for + and minus like
[0..2**L) for positive and [-2**L..0) for negative.

Those half-open sets correspond, so we can just use the absolute value
like abslen here:
--8<---------------cut here---------------start------------->8---
#!/usr/bin/env -S guile --no-auto-compile -e main -s
!#
(use-modules (ice-9 format))

(define (abslen absint)
  (begin
    (let*((absval absint)
    	  (lm (lambda (aval)
    		(begin
    		  (let inner ((n 0) (av aval))
    		    (begin
    	              (if
    	               (< (integer-expt 2 n) av) 
    	               (inner (+ 1 n) av)
    	               n)))))))
	(lm absval))))

(define (main args)
  (begin
    (or
     (false-if-exception 
      (begin
	(display (abslen (abs (string->number (cadr args)))))
	(newline)))
     (begin
       (format #t "\nUsage: ~a NUM -- where NUM is [+ - ] POSITIVE_INTEGER\n" (car args)))
     (newline))))
--8<---------------cut here---------------end--------------->8---

You might want to call the above something other than integer-length,
but it should compute the same result (modulo very limited testing :).

As mentioned in Tom's reply to [1], zero makes for a special problem
in the general mathematical case, where I think you have to special-case
which set of points it should belong to.

In the general case numbers map into half-open annuli in the complex plane,
where inside and outside the unit circle corresponds to x and 1/x, and 1/0
has to be special-cased. The annulus edge circles are at powers of a rational
base, 2 in the binary case, but 4/3 can work. Just not irrationals.
(Maybe as named unit values though?)

Conventional signed number mappings split an annulus in two to map them,
with positives < the splitting circle and negatives >=

Something analogous to abslen can be done to find the power of the base
that will be the diameter of a circle containing (> not >=) both parts
of the split annulus. I haven't done it yet :)

Complex numbers have both cartesian and polar representations, so that
brings in interesting stuff too. The negative of a complex number as
a point in the complex plane is diametrically opposite the origin, but
zero has no direction to an opposite of itself :)
Defining -0 to be 0 has consequences. (Note that fp hardware does
represent -0 :)

You might find it amusing to play with the scheme program
included in [1] (after you inspect it -- no warranties :).

-- 
Regards,
Bengt Richter
PS. Shouldn't euclidean-quotient always produce an exact integer?
(Inexactness if any can be carried by the remainder)





^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2021-07-24 17:12 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
     [not found] <20200421130344.GA9369@LionPure>
     [not found] ` <20200425213350.GA10462@LionPure>
2020-04-28 18:08   ` bug#40744: guile-2.2.4 (integer-length 0) erroneously returns 0, not 1 Björn Höfling
2020-04-28 18:41     ` Björn Höfling
2021-07-16  3:01       ` Rob Browning
2021-07-24 17:12         ` Bengt Richter

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).